It is generally known to manufacture composite structures of planar or plate-shaped panels with a planar or plate-shaped piezoceramic element arranged or sandwiched therebetween. Such composite structures are increasingly being used as components for high velocity actuators, for example such actuators to be used for active noise damping. There is also a hope to develop such composite structures for actuating or controlling the rotors of helicopters.
The known plate-shaped piezoceramic elements that are typically used in such applications, i.e. in high velocity actuators, have a high tension stiffness and compression stiffness, as well as a high compression strength, but a relatively low tensile strength and relatively low achievable active strain. These disadvantages of the known piezoceramic elements make it impossible to successfully use such piezoceramic elements in composite structures for controlling or actuating the rotors of helicopters. Namely, the rotors are subject to substantial tensile strain due to the centrifugal force arising during operation of the rotor, as well as tensile strains resulting from the bending moments. The known piezoceramic elements used in known composite structures are not able to withstand such substantial tensile strains, and thus cannot be used for actuating or controlling the helicopter rotors.